Interpretive Summary: Pseudomonas syringae pv. phaseolicola, a bacterial plant pathogen, causes halo blight of bean. In this study, we report on the genome sequence of P. s. pv. phaseolicola isolate 1448A (1448A). Comparison with another plant pathogen, P. syringae pv. tomato DC3000 (DC3000) revealed many similarities at the gene and genome levels. Although these two bacterial strains are highly similar at the physiological level, they have distinct host ranges (DC3000 causes disease on tomato and Arabidopsis). By examining the five complete pseudomonad genome sequences that are now available, we were able to identify 3,567 genes that likely comprise the core Pseudomonas genome and 365 genes that are syringae-specific.

Technical Abstract:
Pseudomonas syringae pv. phaseolicola, a gram-negative bacterial plant pathogen, is the causal agent of halo blight of bean. In this study, we report on the genome sequence of P. s. pv. phaseolicola isolate 1448A (1448A) which encodes 5,353 open reading frames (ORFs) on one circular chromosome (5,928,787 bp) and two plasmids (131,950 bp and 51,711 bp). Comparative analyses with a phylogenetically divergent pathovar, P. syringae pv. tomato DC3000 (DC3000) revealed a strong degree of conservation at the gene and genome levels. In total, 4,133 ORFs were identified as putative orthologs in these two pathovars using a reciprocal best hit method with 3,941 ORFs present in conserved, syntenic blocks. Although these two pathovars are highly similar at the physiological level, they have distinct host ranges; 1448A causes disease on bean and DC3000 is pathogenic on tomato and Arabidopsis. Examination of the complement of ORFs encoding virulence, fitness, and survival factors revealed a substantial, but not complete, overlap between these two pathovars. Another distinguishing feature between the two pathovars is their distinctive sets of transposable elements. With access to a fifth complete pseudomonad genome sequence, we were able to identify 3,567 ORFs that likely comprise the core Pseudomonas genome and 365 ORFs that are syringae-specific.